LONDON, ENGLAND - FEBRUARY 16: Camilla, Duchess of Cornwall reads during a preview of the new 'Wondercrump World of Roald Dahl' exhibition which celebrates the author's Centenary at the Southbank Centre on February 16, 2016 in London, England. (Photo by Heathcliff O'Malley - WPA Pool/Getty Images)

One farmer is enormously fat, another is boozy and the third is a pot-bellied dwarf. Then there is the grandmother described as 'an old hag' and likened to a witch. This vitriol is not spouted by internet trolls or sparring bogans, but is used by Roald Dahl to describe characters in two of his most popular books, Fantastic Mr Fox and George's Marvelous Medicine.

Dahl pulls no punches in describing his characters' physical and mental shortcomings, regardless of the age or sensitivities of his young readers. And if the sales of the books, which have reached more than 200 million worldwide is anything to judge by, that it is exactly what they want.

In the stage show based on Dahl's book, Matilda sings:

"We're told we have to do what we're told but surely

Sometimes you have to be a little bit naughty."

In rediscovering Dahl's books while reading to my son, I have been surprised by the cheekiness, sometimes bordering on offensiveness, of the language. At a time when children's self-esteem is cushioned with bubble wrap, the brutal depictions of his characters is decidedly un-PC. The fat, the skinny, the short, the tall, the elderly, the smelly and the drunk are all fair game for Dahl.

First, I settled in to read Fantastic Mr Fox to my five-year-old son. Initially, I was uncomfortable reading about the fat, drunk, smelly farmers who were bent on shooting the title character. Is it right to describe someone as 'fat'? Should Dahl be making fun of the tipsy farmer, who clearly had a problem with alcohol? Then I looked over at my son and he was enthralled by the story, seemingly unconcerned by the ridicule of the obese, alcoholic and hygiene-challenged protagonists. And so I relaxed and went with it, albeit with raised eyebrows and an occasional suppressed giggle.

Next, I was surprised about Dahl's descriptions of George's grandma as 'an old hag' and 'a horrid old witchy woman' in George's Marvelous Medicine.

'George couldn't help disliking Grandma. She was a selfish, grumpy old woman. She had pale brown teeth and a small puckered-up mouth like a dog's bottom.'

Wow. It seemed a bit harsh. What if my son started to be disrespectful towards older people in this way or, God forbid, his own grandmother? Should I say something to him; assure him that the elderly were valuable parts of our society and should never be referred to as 'hags', let alone 'grizzly old grunions'?

But I let it go, and believe it or not, while my son listened to the entirety of the story, transfixed, I have yet to hear him refer to his grandmother or any other elderly person in a derogatory way.

Most recently, we started reading The Twits. The book begins with a description of Mr Twit, who has a beard so caked with food that I struggled to read the page about it out loud without gagging. With the proliferation of beards in our suburb and friendship group, this was dynamite. Would my son recoil next time he saw the bearded father of one of his friends?

Then there was Mrs Twit, who was extraordinarily ugly as a result of a life in which her evil thoughts were visible in the ugliness of her face. What a terrible idea, implying that the most beautiful people have the kindest thoughts and that less aesthetically appealing people have thoughts that reflect their ugliness. Really?

But then I continue reading and try to stop over-analysing. I remember reading them as a child and enjoying the very naughtiness that I was now worrying about. And Dahl's books were the only literature my brother read, other than school texts. What a shame it would be for children to miss out on that.

It also helps that many of Dahl's stories have an undercurrent of 'goodness', of the innocent child triumphing over the cruel adult, the weak finding strength and the lonely finding their place in a big, frightening world.

It is a tradition that is carried on proudly by modern young adult writers, with The Day My Bum Went Psycho by Andy Griffiths and Dav Pilkey's Captain Underpants series are obvious examples of the appeal of the subversive for young people. Perhaps, like Matilda, the popularity of these books is indicative of children's and young adults' desire to rebel and step outside the box. To challenge adults' authority and use their own voices.

Perhaps it is even the key to the success of some adult fiction -- would 50 Shades of Grey have been as popular if it didn't seem just a little bit illicit? And some of the joy of Tom Wolfe's Bonfire of the Vanities lies in its unflattering depiction of the rich and powerful.

Throughout history, the knowledge that a book is somehow subversive has only boosted its popularity; the controversial Lady Chatterley's Lover sold hundreds of thousands of copies after it was eventually published, and debate over the moral messaging in The Catcher in the Rye only aided its popularity among rebellious teenagers.

I have to admit that the subversive, un-PC writing, as displayed by Dahl time and time again is a breath of fresh air, even for me, as an adult reader. Sure, Dr Seuss's environmental messages are valuable and the Mr Men series' moral compass is worthy. We all want Mr Rude to get his comeuppance and Mr Sad to cheer up. And I've lost count of the times I've read Share Said the Rooster to my children in the hope that they'll take the message on board. But I think there is still room for the cheeky humour of Roald Dahl. I'll just have to draw the line when he takes aim at tired, cranky mothers.